Along with the development of society and enrichment in material conditions, the linkage between electronic equipment and people's life and work becomes tighter and tighter. Nowadays there are more and more types of electronic equipment such as desktop, laptop, cellular phone and e-book reader. While providing much convenience for people, the electronic equipment may cause leakage of personal information.
For example, a user may usually use the above-described electronic equipment in public places such as in internet bars, in metro or bus, and a display screen of the electronic equipment usually have a relatively wide viewing angle. Therefore, it is not good for protecting personal information security.